Gerrard Butler has revealed that he ‘almost’ killed his co-star on the set of P.S. I Love You.

On Tuesday, Butler came clean on The Drew Barrymore Show, revealing that he accidentally injured actress Hilary Swank in 2007 during a scene in which he danced “like an idiot” in nothing but his underwear and a pair of suspenders.

In the humorous scene, Butler’s character Gerry was supposed to accidentally hit himself in the face with a suspender clip while getting undressed in front of his co-star.

However, the metal attachment “slashed” Swank’s head instead, according to New York Post.

 “It [got] stuck, it release[d] and [flew] over my head,” explained the actor. “I cut her open. You could even see the teeth [of the clip]. She had to get taken to the hospital.”

Butler went on to say that the accessory was “so dangerous” that the camera crew “had plastic fronts to protect themselves” from the flying metal fasteners.

Gerrard Butler accidentally injured Hilary Swank in 2007's P.S. I Love You. Photo / Supplied

The studio emptied “in three seconds” after the incident, leaving a concerned Butler sobbing in his boxers.

“I scarred Hilary Swank. I almost took her eye out, and I just made a fool of myself for two days,” The Ugly Truth star admitted.

Butler then went on to admire his fellow co-star, calling her a “great” person to work with.

In February 2020, news started circling that a P. S. I Love You sequel might be on the horizon.

However, Swank and a few of the film’s co-stars - Kathy Bates, Lisa Kudrow and Harry Connick Jr. - have not yet mentioned whether they will be part of the second instalment.

Butler jested to The Sun in 2016 that he refuses to give his character’s Irish accent a go again, hinting - rather sarcastically - to “all those wonderful reviews and glorious feedback” that he received for the role.

 “I’ve ticked that box,” he added.

As for Hilary Swank, the Million Dollar Baby actress is pregnant and awaiting the arrival of twins with husband Philip Schneider.

The soon-to-be-mum revealed to Page Six that she was feeling “excellent” in her third trimester